Database of Select Committee on GRAS Substances (SCOGS) Reviews

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Tannic acid (hydrolyzable gallotannins)

The Select Committee considers only hydrolyzable gallotannins to be within the definition of tannic acid. Tannic acid yields gallic acid and either glucose or quinic acid as hydrolysis products. These hydrolysis products. These hydrolysis products are consumed as naturally occurring constituents of many foods. The total dietary intake of added tannic acid resulting from its use as a flavoring agent or processing aid can be inferred to be very small. The level of addition of tannic acid to various foods is about 100ppm or less. Thus, the potential level of consumer exposure is orders of magnitude below the lowest levels for which adverse biological effects are reported to occur after oral administration of tannic acid to experimental animals. While the evidence seems clear that food grade tannic acid at concentrations reportedly added to foods is hydrolyzed prior to absortion from the small intestine, the extent and nature of its absorption have not been established for man. In experimental animals, intact tannic acid is apparently absorbed only after mucosal damage caused by large doses of concentrated aqueous tannic acid solutions intubates into empty stomachs or by artificially prolonged exposure of the mucosa to these solutions. Data available to the Select Comittee contain no evidence that tannic acid as currently used in foods can induce mucosal damage. However, toxic effects following parenteral administration to animals suggest that additional studies should be made related to the absorption of tannic acid at dietary levels by individuals with gastrointestinal disorders. Some investigators have reported that daily oral administration of tannic acid to experimental animals by stomach tube for periods of months may cause damage to their liver and other organs similar to that seen after parenteral administration of hydrolyzable tannins to experimentals animals, and to that reported historically in man following topical treatment of burns with tannic acid. None of these effects is reported, however, in experimental animals receiving tannic acid as a component of their ration, even at levels of several percent of the diet. Nevertheless, the reported hepatocarcinogenic effect of parenterally injected hydrolyzable gallotannins is of concern to the Select Committee owing, in part, to the lack of uniformity of composition and sources of the preparations used in the tests available in the literature for evaluation. While the evidence available to the Select Committe does not demonstrate hazard of carcinogenicity inherent in food grade tannic acid, research is needed to answer the question of why there are such extreme differences between the results of parenterally and orally administered hydrolyzable tannins in rodents. There is no evidence of a clear and present danger to the public health occasioned by the current use of dietary tannic acid as a food ingredient. The Select Commitee, therefore, in the light of the foregoing concludes that: There is no evidence in the available information on tannic acid (hydrolyzable gallotannins) that demonstrates or suggests reasonable grounds to suspect a hazard to the public when it is used at levels that are now current and in the manner now practiced. However, it is not possible to determine, without additional data, whether a significant increase in consumption would constitute a dietary hazard.